Tft liquid cyrstal display panel using micro lens array and manufacturing method thereof

ABSTRACT

The present invention is related to the liquid crystal display panel using micro lens array and manufacturing method thereof, the present invention comprising; first step for forming photoresist in regular interval on first transparent substrate; second step for forming a certain size groove to etch regular interval; third step for eliminating impurities and photoresist on first transparent substrate; and fourth step for union first transparent substrate and second transparent substrate to use direct bonding method.

TECHNICAL FIELD

The present invention generally relates to a TFT liquid crystal displaypanel used for a liquid crystal projector and a manufacturing methodthereof, and more specifically, to a TFT liquid crystal display panelusing a micro lens array formed by forming lenses between two sheets oftransparent substrates and coupling the two sheets of the transparentsubstrates through a direct bonding process and a manufacturing methodthereof.

BACKGROUND ART

Generally, a liquid crystal display panel displays images bytransmitting or cutting off light, and can brightly display the imageswhen there is much transmitted light.

A degree of the transmitted light is called an opening ratio, whichshows a ratio of light passing through the liquid crystal display panelamong irradiated lights. As higher the opening ratio is, a brighterimage is displayed. Thus, the liquid crystal display panel can displaythe image to be more harmonized with natural colors.

In order to improve the opening ratio, a method of using a micro lensarray has been suggested, which enabled light incident on a lightcut-off region to be refracted by using the micro lens array and beirradiated to a light transmission region. As a result, when the samebright light source is used, a brighter image is displayed since muchlight is transmitted in the light transmission region.

FIG. 1 is a diagram illustrating a sectional view in accordance with amanufacturing process of a micro lens array by prior art. Referring toFIG. 1, pattern photo registers (11) on a transparent substrate (10)(a), then the photo registers (11) are formed as many consecutiveconvexly-curved surfaces on the transparent substrate (0) by beingreflowed. When an upper part of the transparent substrate is dry-etched,many convex lens-shaped flexions are formed in the upper part of thetransparent substrate (10) (c). Then, a synthetic resin (12) is smoothlycoated in the upper part of the transparent substrate (110), where theconvex lens-shaped flexions are formed.

Since the synthetic resin and the flexions of the transparent substratebecome micro lenses, respectively, by refraction index differencesbetween the synthetic resin (12) and the transparent substrate (10), amicro lens array consisting of the micro lenses is formed in the upperpart of the transparent substrate.

Also, a dustproof substrate (20) is attached to the upper part of thetransparent substrate where the micro lens array is formed (e).

The reason why the dustproof substrate is attached to such micro lensarray is as follows: when a liquid crystal display panel expands adisplayed image on a projection lens and displays the expanded image ona screen, the projection lens focuses on the liquid crystal displaypanel; at this time, if foreign substance such as dust is attached to asurface of the liquid crystal display panel, the foreign substance isexpanded by the projection lens due to the thin liquid crystal displaypanel and is displayed like an image on the screen. To solve the aboveproblem, the dustproof substrate is attached to both sides of the liquidcrystal display panel, to make the liquid crystal display panel thick.Accordingly, even though foreign substance such as dust is attached tothe surface of the liquid crystal display panel, the foreign substanceis separated from a focus of the projection lens at more than a certaindistance, thereby preventing the foreign substance such as dust frombeing shown on the screen.

In addition, when light is irradiated on the liquid crystal displaypanel, it causes heat on the liquid crystal display panel. On thisoccasion, if excessive heat is generated thereon, there produces adisplaying problem on the liquid crystal display panel. Therefore, it isnecessary for the liquid crystal display panel to stand the heat byattaching the dustproof substrate thereto and distributing the heatgenerated on the liquid crystal display panel.

However, a prior micro lens array is manufactured by using a syntheticresin, which is weak in heat. A TFT liquid crystal device has atransparent electrode with the use of an ITO (Indium Tin Oxide). Toobtain a high-quality transparent electrode, it should be processed atmore than 230° C., approximately. On the other hand, since the syntheticresin does not stand high temperature like 230° C. above, it isessential to form the transparent electrode in the micro lens arrayincluding the synthetic resin at about 180˜200° C. by using an LT (LowTemperature) ITO processing method. So, it is impossible to form thehigh-quality transparent electrode, resulting in transmittancedeterioration of the transparent electrode and an increase ofresistance.

Furthermore, the prior micro lens array using the synthetic resin hasdifficulty in cutting as well.

Generally, a scribe breaking method is used to cut the micro lens array.That is, after flawing an upper side of glass (or quartz) by scratchingit in a position to be cut, cut an upper part of the flawed side by avertical force in vertical direction to the upper side. The verticalforce is transmitted in vertical direction to the upper side on theglass (or quartz), but the direction of the vertical force is changed ina region of the synthetic resin (12), preventing the cut side from beingvertically formed. Therefore, according to the prior micro lens array,it is unavailable to apply a manufacturing method for cutting the microlens array in a post process after attaching the micro lens array to theliquid crystal panel having a TFT element.

And, because the dustproof substrate is attached to the transparentsubstrate by using the synthetic resin, there is a possibility ofchanging cell gaps of the liquid crystal display panel owing todifferent thermal expansion coefficients of the synthetic resin, thedustproof substrate, and the transparent substrate when heat is applied.Also, an additional operation such as a process for attaching thedustproof substrate is required, making a process of manufacturing theliquid crystal display panel complex at high price.

Moreover, light transmittance of the liquid crystal display panel maydeteriorate due to an adhesive, with a possibility of attaching foreignsubstance while attaching the dustproof substrate to the liquid crystaldisplay panel. Accordingly, it causes various problems such as increasedcosts with managerial difficulty for preventing the above shortcomings,as well as removal of bubbles and folds.

In addition, since the synthetic resin used to form the micro lens arrayhas temperature limits, it is impossible to adopt a method for applyinga transparent electrode at temperature which a general transparentelectrode is applied to.

DISCLOSURE OF INVENTION

It is therefore an object of the present invention to provide a microlens array that freely performs a cell cutting operation and does notrestrict a transparent electrode forming process at low temperature,without using another optical adhesive, a liquid crystal panel using thesame, and a manufacturing method thereof. It is another object of thepresent invention to provide a TFT liquid crystal display panel using amicro lens array formed without attaching another dustproof substratethereto when a thick transparent substrate is used to form the microlens array and a manufacturing method thereof.

To accomplish the above object, the present invention comprises a firststep of consecutively forming photo registers on a first transparentsubstrate, said each photo register being separated at predeterminedinterval; a second step of forming grooves with predetermined size on anupper part of the first transparent substrate by etching thepredetermined intervals formed between the photo registers; a third stepof removing impurities remaining on the upper part of the firsttransparent substrate and the photo registers; and a fourth step ofuniting a second transparent substrate with the upper part of the firsttransparent substrate by a direct bonding method; wherein the firsttransparent and the second transparent substrate are made of samematerial.

At this time, it is desirable to perform a wet etching process for theetching process carried out in the above manufacturing method, and isdesirable to add a process of patterning a transparent conductive filmor a process of grinding the transparent substrate after the directbonding process.

Also, to accomplish the above object, the present invention comprisesthe steps of: a first step of reflowing photo registers to make them inspherical shape after consecutively forming the photo registers on afirst transparent substrate, being separated at predetermined intervals;a second step of forming grooves having predetermined size in an upperpart of the first transparent substrate by etching the predeterminedintervals formed between the reflowed photo registers; a third step ofremoving impurities remaining in the upper part of the first transparentsubstrate and the photo registers; and a fourth step of uniting a secondtransparent substrate with the upper part of the first transparentsubstrate by a direct bonding method. The first transparent substrateand the second transparent substrate are made of the same material.

On this occasion, it is available to use either of a wet etching or adry etching process for the etching process performed in the abovemanufacturing method, and is desirable to add a process of patterning atransparent conductive film or a process of grinding the transparentsubstrate after carrying out the direct bonding process.

To carry out another object, in a micro lens array refracting lightincident on a light cut-off region to a light transmission region, thepresent invention comprises: a first transparent substrate; a secondtransparent substrate united with the first transparent substrate in adirect bonding method without using another adhesive; and groovesdisposed on at least one side of the first transparent substrate and thesecond transparent substrate in a region where the first transparentsubstrate and the second transparent substrate are united together, andconsecutively formed in certain size. The first transparent substrateand the second transparent substrate are made of the same material.

The above micro lens array improves an opening ratio by being attachedto a liquid crystal panel, thereby enabling a liquid crystal displaydevice to be manufactured with better picture quality.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a diagram illustrating a sectional view in accordance with amanufacturing process of a micro lens array by prior art.

FIG. 2 is a process flow chart of a micro lens array manufacturingprocess in accordance with one embodiment of the present invention.

FIG. 3 is a diagram illustrating a sectional view of a manufacturingprocess of a micro lens array in accordance with one embodiment of thepresent invention.

FIG. 4 is a process flow chart of a micro lens array manufacturingprocess in accordance with another embodiment of the present invention.

FIG. 5 is a diagram illustrating a sectional view of a manufacturingprocess of a micro lens array in accordance with another embodiment ofthe present invention.

BEST MODE FOR CARRING OUT THE INVENTION

The present invention will be described in detail through preferredembodiments with reference to accompanying drawings, compared to priorart.

As one embodiment of a micro lens array in accordance with the presentinvention, FIG. 2 is a flow chart illustrating a manufacturing process,and FIG. 3 is a diagram illustrating a sectional view in accordance witha manufacturing process of a micro lens array. The present invention nowwill be described in reference to FIG. 2 and FIG. 3 as follows.

A first step (ST 100): By reflowing after applying and patterning photoresisters (110) on a thick transparent substrate (100), the photoregisters (110) on the transparent substrate (100) are consecutivelyformed with patterns having convex curved surfaces like circular convexlens shapes on upper parts of pixels (drawing 3 a). At this time, theformed photo registers (110) are about 10˜20 um in size, and gapsbetween the photo registers (110) are about 0.8 um in size. They areshown on the drawing just for convenience sake.

When the transparent substrate (100) gets thicker, first it can standheat by distributing the heat generated from light irradiated from alight source on the transparent substrate (100). Second, it isunnecessary to use a dustproof substrate by separating foreign substancesuch as dust attached to the transparent substrate (100) from a focaldistance of a lens at more than a certain distance, since the focaldistance of the lens expanding an image on a projector for displayingthe image with the use of a liquid crystal display panel is adjusted toa liquid crystal layer.

Thickness of the transparent substrate (100) should be controlled inorder to assemble and use by a manufacturing equipment of an existingliquid crystal display panel.

If the transparent substrate is thin, it is ineffective to preventforeign substance from being displayed because the foreign substance isnear to a focus of a projection lens. On the other hand, if too thick,it is difficult to assemble the transparent substrate by using anexisting manufacturing equipment even though a screen is little affectedby foreign substance, with a possibility of transmitted light beingreduced. Thus, it is desirable for the transparent substrate to be about1.3 mm and 2.5 mm in thickness.

A second step (ST 110): Partially etch the upper part of the transparentsubstrate (100) where the photo registers (110) having the convex curvedsurfaces are applied. When a dry etching process is applied, perform theetching process after forming the photo registers (110) in convex lensshape itself by reflowing the photo registers. In case of a wet etchingprocess, form a lens shape at a desirous angle by wet-etching generalpatterns. For the dry etching process, an etched region is a part whereheight of the photo registers (110) is lowest, and is an external partof each convex curved surface.

So, grooves having certain curved surfaces are formed in a region whereexternal parts of convex curved surfaces of the transparent substrate(100) are located. Since each groove is formed in the external parts ofthe convex curved surfaces, each groove is connected together in aneighboring part through the convex curved surfaces (drawing 3 b). Thephoto registers (110) remain in a region where the dry etching processis not carried out.

A third step (ST 120): Many grooves are formed with certain curvedsurfaces in the upper part of the flat transparent substrate (100) whenthe photo registers remaining on the transparent substrate (100) andimpurities are removed through ashing/strip processes. As a modelexample of the ashing/strip processes, remove the photo registers byusing O2 plasma, and strip the still remaining photo registers,impurities, and a polymer with the use of sulphuric acid.

A fourth step (ST 130): Unit a cover glass (150) with the upper part ofthe transparent substrate (100) where the grooves are formed (drawing 3c). At this moment, the united cover glass (150) should be made of thesame material as that of the transparent substrate (100) because adirect bonding method is used. That is, if the transparent substrate(100) is made of quartz, the cover glass (150) should be made of thesame material, and if the transparent substrate (100) is made of glasscontaining a UV blocker, the cover glass (150) should be made of thesame glass containing the UV blocker.

A direct bonding process is used for a process of attaching the coverglass (150) to the upper part of the transparent substrate (100) inaccordance with the present invention. Though there is a difference inconditions depending on bonding materials, the cover glass (100) isgenerally attached to the transparent substrate (50) where the groovesare formed, without using an adhesive, through a surface control processof attaching the cover glass by controlling an adhered surface state.The present invention does not use any adhesive by directly attachingthe cover glass (150) to the transparent substrate (100). As a result,it can solve a problem of generating bubbles caused when applying theadhesive.

Gas filled inside of the grooves is differentiated, depending on asurrounding environment under which a direct bonding process isperformed. In case the direct bonding process is performed in the air,the air is filled. And, if the process is carried out in a vacuum state,the vacuum state is maintained. Thus, the gas filled inside of thegrooves has a different refractive index from that of the transparentsubstrate (100) and the cover glass (150).

Then, the grooves formed in the upper part of the transparent substrate(100) are connected together, and the transparent substrate (100) isattached to the cover glass (150) in parallel, thereby enabling thegrooves formed on the transparent substrate (100) to become poresthrough which the air passes. The pores easily emit heat generated froma liquid crystal display.

In addition, most regions of the transparent substrate (100) are flat.Thus, a path of vertically incident light is not changed since the lightpasses without being refracted, by closely adhering the transparentsubstrate (100) to the cover glass (150) in parallel. However, since thegrooves formed on the transparent substrate (100) are separated from thecover glass (150) at certain intervals, the incident light is refracteddue to a difference between the air of pores disposed between the coverglass (150) and the transparent substrate (100) and curved surfaces ofthe formed grooves. Therefore, light is refracted according to Snell'slaw shown in a mathematical formula 1 by the curved surfaces of thegrooves and a refractive index difference of the air and the transparentsubstrate due to the refraction of the light. Accordingly, regions wherethe grooves are formed play a role of a convex lens, thereby refractinglight irradiated to the regions and making the refracted light incidenton a region having a flat surface.

For a path of passing light vertically incident on the upper part of thetransparent substrate (100), most incident light is not refracted andvertically passes through the transparent substrate (100) and the coverglass (150), since most upper parts of a lens are planarized while thetransparent substrate (100) and the cover glass (150) are attachedtogether in parallel. However, a path of light passing through remainingcurved surfaces by a spherical edge part plays a role of the lens due toa refractive index difference between the air and the transparentsubstrate and flexions of the curved surfaces, refracting lightaccording to the Snell's law shown in the mathematical formula 1.Therefore, it is possible to increase an opening ratio of a liquidcrystal display panel by locating a light transmission region of aliquid crystal display in a region where the transparent substrate isclosely adhered to the cover glass and locating a light cut-off regionof the liquid crystal display in a part where the grooves are formed.$\begin{matrix}{\frac{\sin\quad\theta_{1}}{\sin\quad\theta_{2}} = \frac{n_{2}}{n_{1}}} & \left\lbrack {{Mathematical}\quad{formula}\quad 1} \right\rbrack\end{matrix}$

A fifth step (ST 140): Grind at least one surface selected from theunited transparent substrate (100) and the cover glass (150) (drawing 3d). Since it is hard to handle too thin glass or a thin quartz substrateowing to its weak strength, unnecessary thickness is grinded aftercarrying out the uniting process by using relatively thick glass or athick quartz substrate. On this occasion, it is desirable for thesubstrate to maintain 50 to 100 um in thickness after the grindingprocess.

A sixth step (ST 150): Apply a transparent electrode (160) at more thanhigh temperature 200° C. to an external surface of the grinded substrateon the transparent substrate (100) or the cover glass (150) (drawing 3e). The reason why the transparent electrode is applied at more thanhigh temperature 200° C. is because there are no thermal restrictionsincluding a problem of melting a synthetic resin by heat, because thesynthetic resin is not used as an adhesive unlike prior art.

According to the prior art, the transparent electrode is applied at lowtemperature because there is a possibility of transforming the syntheticresin by heat at high temperature. However, in case of the presentinvention, the cover glass (150) is directly attached to the transparentsubstrate (100), without using a material such as the synthetic resinthat is transformed by temperature. Thus, it is available to apply thetransparent electrode at high temperature, enabling the transparentelectrode to be applied at 230° C.

For another embodiment of a micro lens array in accordance with thepresent invention, FIG. 4 is a flow chart illustrating a manufacturingprocess, and FIG. 5 is a diagram illustrating a sectional view inaccordance with a manufacturing process of a micro lens array. Thepresent invention will be described in reference to FIG. 4 and FIG. 5 asfollows.

A first step (ST 200): Apply photo registers (110) on a thicktransparent substrate (100), and pattern them (drawing 5 a). The formedphoto registers (110) are about 10˜20 um in thickness (d1), gaps betweenthe photo registers (110) are about 0.8 um in thickness (d2), and theyare shown on the drawing just for convenience sake.

A second step (ST 210): Partially etch an upper part of the transparentsubstrate (100) where the photo registers (110) are applied. In thepresent embodiment, a wet etching process is carried out because thephoto registers (110) are not reflowed. The wet etching process uses abuffer oxide echant.

So, grooves having certain curved surfaces are formed on the transparentsubstrate (100) (drawing 5 b). Then, the photo registers (110) remain ina region where the etching process is not performed. Like shown in adiagram expanding inside of a circle in FIG. 5, it is desirable to formthe grooves at about 15˜20° on the transparent substrate (100) in orderto improve an opening ratio.

A third step (ST 220): Many grooves are formed with certain curvedsurfaces in an upper part of the transparent substrate (100), when thephoto registers remaining on the transparent substrate (100) andimpurities are removed through ashing/strip processes. As a modelexample of the ashing/strip processes, remove the photo registers byusing 02 plasma, and strip the still remaining photo registers,impurities, and a polymer with the use of sulphuric acid.

A fourth step (ST 230): Unite a cover glass (150) with the upper part ofthe transparent substrate (100) where the grooves are formed (drawing 5c). At this time, the united cover glass (150) should be made of thesame material as that of the transparent substrate (100) since a directbonding method is used. That is, if the transparent substrate (100) ismade of quartz, the cover glass (150) should be made of the samematerial, and if the transparent substrate (100) is made of glasscontaining a UV blocker, the cover glass (150) should be made of thesame glass containing the UV blocker.

A fifth step (ST 240): Grind at least one surface selected from theunited transparent substrate (100) and the cover glass (150) (drawing 5d). Since it is hard to handle too thin glass or a thin quartz substrateowing to its weak strength, unnecessary thickness is grinded aftercarrying out the uniting process by using relatively thick glass or athick quartz substrate.

A sixth step (ST 250): Apply a transparent electrode (160) at more thanhigh temperature 200° C. to an external surface of the grinded substrateon the transparent substrate (100) or the cover glass (150) (drawing 5e).

INDUSTRIAL APPLICABILITY

According to a TFT liquid crystal display panel using a micro lens arrayformed in accordance with the present invention and a manufacturingmethod thereof, it is possible to perform other processes at hightemperature since an adhesive such as a sort of a synthetic resin is notused while manufacturing the micro lens array. Thus, it can use aprocess of forming a transparent electrode by using an ITO requiringabout 230° C., thereby forming a high-quality transparent electrodehaving good transmittance and conductivity.

Furthermore, it is easy to cut the micro lens array, because a syntheticresin is not used. Accordingly, it is available to perform amanufacturing method for cutting the micro lens array in a post processafter attaching the micro lens array to a liquid crystal panel having aTFT element.

And, if either of transparent substrates used to manufacture the microlens array is thick, it is unnecessary to attach a dustproof substrate.Therefore, it can simplify a manufacturing process of the micro lensarray by omitting a process of attaching the dustproof substrate, aswell as prevent transmittance from deteriorating by an adhesive.

Moreover, since pores are formed inside of the transparent substratewhere the micro lens array is formed, external air is directly contactedwith inside of the micro lens array through the pores, thereby easilyemitting heat generated from a liquid crystal display panel through theair. As a result, a liquid crystal projector using the liquid crystaldisplay panel to which the micro lens array is attached in accordancewith the present invention can easily emit heat. So, compared to anexisting liquid crystal projector, it is possible to use a smallercooling device, reducing weight and size of the liquid crystalprojector.

This invention may, however, be embodied in different forms and shouldnot be construed as limited to the embodiments set forth herein. Rather,these embodiments are provided so that this disclosure will be thoroughand complete, and will fully convey the scope of the invention to thatskilled art.

1. A method of manufacturing a micro lens array, said method comprising:a first step of consecutively forming photoresists on a firsttransparent substrate, each photoresist being separated by an interval;a second step of forming grooves on an upper part of the firsttransparent substrate by etching the intervals formed between thephotoresist; a third step of removing impurities remaining on the upperpart of the first transparent substrate and the photoresists; and afourth step of uniting a second transparent substrate with the upperpart of the first transparent substrate by a direct bonding method;wherein the first transparent and the second transparent substrate aremade of the same material.
 2. The method of claim 1, said method furthercomprising a fifth step of grinding at least one of the firsttransparent substrate and the second transparent substrate after thefourth step.
 3. The method of claim 1, wherein the etching processperformed at the second step is carried out by a wet etching process. 4.The method of claim 2, said method further comprising a sixth step ofpatterning a transparent electrode on at least one external surfaceselected from the first transparent substrate or the second transparentsubstrate.
 5. A method of manufacturing a micro lens array, comprising:a first step of making photoresists in spherical shape by reflowing themafter consecutively forming the photoresists on a first transparentsubstrate, said photoresists being separated at predetermined intervals;a second step of forming grooves with predetermined size in an upperpart of the first transparent substrate by etching the predeterminedintervals, said intervals formed between the reflowed photoresists; athird step of removing impurities remaining in the upper part of thefirst transparent substrate and the photoresists; and a fourth step ofuniting a second transparent substrate with the upper part of the firsttransparent substrate by a direct bonding method.
 6. The method of claim5, said method further comprising a fifth step of grinding at least oneof the first transparent substrate and the second transparent substrateafter the fourth step.
 7. The method of claim 6, said method furthercomprising a sixth step of patterning a transparent electrode on atleast one external surface selected from the first transparent substrateor the second transparent substrate.
 8. A micro lens array refractinglight incident in a light cut-off region to a light transmission region,comprising: a first transparent substrate; a second transparentsubstrate being united with the first transparent substrate by a directbonding method without using another adhesive; and grooves disposed in aregion where the first transparent substrate and the second transparentsubstrate are united together and consecutively formed in certain size,said grooves formed on at least one side of the united first transparentsubstrate and the second transparent substrate.
 9. The micro lens arrayof claim 8, wherein the grooves having slopes, and an angle between theslopes and an upper surface of the transparent substrate beingmaintained at 15 to 20 degrees.
 10. The micro lens array of claim 8,wherein the first transparent substrate and the second transparentsubstrate being made of quartz or glass containing a UV blocker.
 11. Themicro lens array of claim 8, wherein a patterned transparent electrodebeing further comprised on an external side of the first transparentsubstrate or the second transparent substrate.
 12. A liquid crystalpanel having a micro lens array according to claim
 10. 13. A liquidcrystal display device having a micro lens array according to claim 10.14. The method of claim 1, wherein the photoresists are separated byintervals of about 0.8 μm.
 15. The method of claim 1, wherein thephotoresists are about 10 to 20 μm in size.